The present invention relates to PBX (Private Branch Exchange) equipment connected to a TELEPHONE COMPANY Central Office (CO) using Direct-In-Dialing (DID) trunk lines and/or E&M tie lines, where the PBX is in turn connected to a Voice Message System (VMS).
A PBX can be defined as a telephone exchange serving a single organization, having incoming and outgoing trunk lines from a Central Office, and extension lines connected to telephone extensions on the customer's premises. The PBX equipment provides for switching calls from the incoming lines to any of the extensions, switching calls between any two extensions, and switching calls between extensions and outgoing trunk lines to the CO. In most cases, a PBX has an attendant's console, which is used to extend incoming trunk line calls to extension lines. PBX equipment is, of course, well known in the prior art, as numerous manufacturers are providing many types of equipment for virtually every type of business environment.
A DID trunk line is a special facility available from the telephone company Central Office that requires special equipment in the CO and special DID trunk interfaces on the associated PBX. With DID, a party outside the PBX can call an extension in the PBX directly without going through the attendant's console. The outside party dials a 7- or 10-digit (the outside party may need to dial a "1" in front of area code) number, of which the last 3 or 4 digits are the actual extension number on the PBX. When the CO receives a call that is destined to a PBX with DID, it will signal or "pulse" the last 3 or 4 digits to the PBX over the DID trunk line to signal which extension to ring. The PBX receives these "pulsed" digits over its DID interface and connects the incoming DID trunk directly to try to ring the desired telephone extension.
An E&M tie trunk is used to connect two PBX's or a PBX to a tandem switch. An E&M tie line permits a user in one location to directly call those in another location without using the public switched network. The PBX's must be equipped with special E&M tie line interface circuits to connect to the E&M tie lines. The PBX receiving an incoming call over an E&M tie line will receive the digits corresponding to the extension being called. These digits can be received as "pulses" on the "E" lead or Dual Tone Multi-Frequency (DTMF) inband tone signals on the voice leads.
A Voice Message System (VMS) can be connected to a PBX and is used to record voice messages for specified users in what is known as the users' "mailbox." In most cases, the caller uses a Dual Tone Multi-Frequency (DTMF or "Touch Tone") telephone to enter the mailbox or extension number of the person the caller wishes to leave a message for. There is a need to use a VMS to record a message when a call to a particular telephone extension on the PBX is not answered or is busy.
In the current art, this can be done by instructing the PBX, on busy or ring-no-answer calls to an extension, to forward the call to another group of extensions. Connected to this group of extensions are the ports of a VMS. When the VMS receives a call, it will prompt with something like "YOU HAVE REACHED THE ABC COMPANY MESSAGE CENTER, PLEASE RE-ENTER THE LAST THREE DIGITS OF THE NUMBER YOU WERE TRYING TO REACH." If the caller has a DTMF-equipped phone, he enters what is essentially the extension number he was trying to call, and the VMS can then record a message to be stored in the voice mailbox corresponding to that extension. There are several problems with this method.
First, some PBX's do not support forwarding of calls on busy and/or ring-no-answer to a group of extensions; second, the caller finds it awkward and inconvenient to have to enter the extension number; and third, the caller may have a rotary dial phone, in which case the VMS cannot receive the extension number.
In some cases, the PBX software program can be modified to automatically send the called station identification to the VMS when a call to a called extension is ring-no-answer or busy forwarded. However, this requires the cooperation of the PBX manufacturer and modification of the PBX, and is rare.
It would therefore be desirable to provide an apparatus and a method to operate on any PBX using DID incoming trunk lines or E&M tie lines and a Voice Message System, such that when the extension called by an incoming DID trunk line or E&M tie line does not answer or is busy, the line will be automatically connected to the Voice Message System, and the called station extension number will be automatically sent in DTMF format to the VMS, so a message can be recorded for the specific called party and then the message can be put in the proper "mailbox" associated with the desired extension number.